حمض التلوريك

حمض التلوريك
Skeletal formula of ortho-telluric acid
Ball-and-stick model of ortho-telluric acid
الأسماء
اسم أيوپاك
Hexahydroxidotellurium
أسماء أخرى
Orthotelluric acid, Tellurium(VI) hydroxide
المُعرِّفات
رقم CAS
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.029.334 Edit this at Wikidata
UNII
الخصائص
الصيغة الجزيئية Te(OH)
6
كتلة مولية 229.64 g/mol
المظهر White monoclinic crystals
الكثافة 3.07 g/cm3
نقطة الانصهار
قابلية الذوبان في الماء 50.1 g/100 ml at 30 °C[1]
الحموضة (pKa) 7.68, 11.0 at 18 °C[1]
البنية
الشكل الجزيئي octahedral
Dipole moment 0 D
المخاطر
خطر رئيسي corrosive
مركبات ذا علاقة
Hydrotelluric acid
Tellurous acid
Hydrogen telluride
مركـّبات ذات علاقة
Teflic acid
Sulfuric acid
Selenic acid
ما لم يُذكر غير ذلك، البيانات المعطاة للمواد في حالاتهم العيارية (عند 25 °س [77 °ف]، 100 kPa).
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مراجع الجدول

حمض التلوريك Telluric acid هو مركب كيميائي صيغته Te(OH)
6
. وهو صلب أبيض معمول من جزيئات Te(OH)
6
ثمانية الأسطح which persist in aqueous solution.[2] There are two forms, rhombohedral and monoclinic, and both contain octahedral Te(OH)
6
molecules.[3] Telluric acid is a weak acid which is dibasic, forming tellurate salts with strong bases and hydrogen tellurate salts with weaker bases or upon hydrolysis of tellurates in water.[3][4] It is used as tellurium-source in the synthesis of oxidation catalysts.[5][6][7]

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

التحضير

Telluric acid is formed by the oxidation of tellurium or tellurium dioxide with a powerful oxidising agent such as hydrogen peroxide, chromium trioxide or sodium peroxide.[3]

TeO
2
+ H
2
O
2
+ 2 H
2
O → Te(OH)
6

Crystallization of telluric acid solutions below 10 °C gives Te(OH)
6
·4H2O
.[2] It is oxidizing, as shown by the electrode potential for the reaction below, although it is kinetically slow in its oxidations.[3]

H
6
TeO
6
+ 2 H+
+ 2 e
⇌ TeO
2
+ 4 H
2
O
, Eo = +1.02 V

Chlorine, by comparison, is +1.36 V and selenous acid is +0.74 V in oxidizing conditions.


الخصائص والتفاعلات

The anhydrous acid is stable in air at 100 °C but above this it dehydrates to form polymetatelluric acid, a white hygroscopic powder (approximate composition (H
2
TeO
4
)
10
), and allotelluric acid, an acid syrup of unknown structure (approximate composition (H
2
TeO
4
)
3
(H
2
O)
4
).[8][2]

Typical salts of the acid contains the anions [Te(O)(OH)
5
]
and [Te(O)
2
(OH)
4
]2−
. The presence of the tellurate ion TeO2−
4
has been confirmed in the solid state structure of Rb
6
[TeO
5
][TeO
4
]
.[9] Strong heating at over 300 °C produces the α crystalline modification of tellurium trioxide, α-TeO
3
. [4] Reaction with diazomethane gives the hexamethyl ester, Te(OCH
3
)
6
.[2]

Telluric acid and its salts mostly contain hexacoordinate tellurium.[3] This is true even for salts such as magnesium tellurate, MgTeO
4
, which is isostructural with magnesium molybdate and contains TeO
6
octahedra.[3]

أشكال أخرى من حمض التلوريك

Metatelluric acid, H
2
TeO
4
, the tellurium analogue of sulfuric acid, H
2
SO
4
, is unknown. Allotelluric acid of approximate composition (H
2
TeO
4
)
3
(H
2
O)
4
, is not well characterised and may be a mixture of Te(OH)
6
and (H
2
TeO
4
)
n
.[2]

أحماض التلوريوم الأخرى

Tellurous acid H
2
TeO
3
, containing tellurium in its +4 oxidation state, is known but not well characterised. Hydrogen telluride is an unstable gas that forms hydrotelluric acid upon addition to water.

المراجع

  1. ^ أ ب Lide, David R. (1998), Handbook of Chemistry and Physics (87 ed.), Boca Raton, Florida: CRC Press, ISBN 0-8493-0594-2 
  2. ^ أ ب ت ث ج Greenwood, N. N. (1997). Chemistry of the Elements (2nd Edition ed.). Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4. {{cite book}}: |edition= has extra text (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  3. ^ أ ب ت ث ج ح قالب:Cotton&Wilkinson6th
  4. ^ أ ب Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
  5. ^ "Surface chemistry of phase-pure M1 MoVTeNb oxide during operation in selective oxidation of propane to acrylic acid". J. Catal. 285: 48–60. 2012.
  6. ^ "Multifunctionality of Crystalline MoV(TeNb) M1 Oxide Catalysts in Selective Oxidation of Propane and Benzyl Alcohol". ACS Catalysis. 3: 1103–1113. 2013.
  7. ^ Yun, Yang Sik; Lee, Minzae; Sung, Jongbaek; Yun, Danim; Kim, Tae Yong; Park, Hongseok; Lee, Kyung Rok; Song, Chyan Kyung; Kim, Younhwa; Lee, Joongwon; Seo, Young-Jong (2018-12-05). "Promoting effect of cerium on MoVTeNb mixed oxide catalyst for oxidative dehydrogenation of ethane to ethylene". Applied Catalysis B: Environmental (in الإنجليزية). 237: 554–562. doi:10.1016/j.apcatb.2018.06.025. ISSN 0926-3373.
  8. ^ Loub, J.; Haase, W.; Mergehenn, R. (1979). "Structure of an adduct of orthotelluric acid and urea". Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry. 35 (12): 3039–3041. doi:10.1107/S0567740879011286.
  9. ^ Catherine E. Housecroft; Alan G. Sharpe (2008). "Chapter 16: The group 16 elements". Inorganic Chemistry, 3rd Edition. Pearson. p. 526. ISBN 978-0-13-175553-6.